Detection and measurement of wave breaking - Breaking and Dissipation of Ocean Surface Waves - page 102

Figure 3.13 Lake George sample results. Vertical bars indicate breaking events. (top) Surface
elevations. (middle) Instantaneous amplitude a (2.60) . (bottom) Instantaneous spectrum-average
frequency ω (2.60) . Figure is reproduced from Liu&Babanin ( 2004 ) (copyright of Copernicus
Publications on behalf of the European Geosciences Union)

2005 ), and here we will only summarise relevant details of the Black Sea data set and
observations.
The Black Sea is a large enclosed water body, extending some 1200 km west-east and
more than 400 km north-south ( Figure 3.14 ). Most of the sea is over 1000 m deep, and
therefore wind-waves develop in ocean-like conditions. A major difference, compared to
the ocean, is the rarity of swell in the Black Sea because of its enclosed location, and
absence of strong surface currents. This makes the Black Sea a convenient site for field
observations of deep-water waves in their relatively pure state, not perturbed by wave-
swell and wave-current interactions.
Four wind-wave records analysed by Liu & Babanin ( 2004 ) with the purpose of devel-
oping a wavelet-based breaking-detection procedure were taken from an oil rig situated
on the 30m-deep sea shelf in the northwest region of the Black Sea ( Figure 3.14 ). Fetch
and depth environment constituted ideal deep-water development conditions, with peak
frequencies f p

= 0 . 16-0 . 27 Hz (wavelengths λ p ≈ 20-60m), significant wave heights

H s ∼ 1m, wind speeds U 10 = 8 . 7-10 . 7m / s and mature-wave development stages of

U 10 / 7. A brief summary of relevant wind-wave properties is provided in the last

four records of Table 5.1 .

c p = 1-1 .